Those display panel or device substrates for use in active matrix type liquid crystal display devices and organic EL display devices, color filter substrates, solar cell substrates and the like which are made of glass are generally in wide use. In recent years, however, for the reasons that glass sheets are breakable, inflexible, and unsuited to weight reduction, various plastics materials have been investigated as substitutes therefor.
For example, Laid-open Japanese Patent Application (JP Kokai) H10-77321 describes that a member obtained by curing a resin composition comprising a noncrystalline thermoplastic resin and an actinic radiation-curable bis(meth)acrylate with an actinic ray can be used as a substitute for a glass substrate, such as a liquid crystal panel substrate. Further, JP Kokai H10-90667 describes a liquid crystal display device in which a transparent substrate obtained by curing/molding a composition comprising a specific alicyclic-structured or aromatic bis(meth)acrylate with an actinic radiation or the like is used.
However, these known plastics materials as substitutes for glass are all high in coefficient of linear expansion as compared with glass sheets and, when used as display device substrates, in particular active matrix display device substrates, they may cause such troubles as warping and aluminum wiring breaking in the production process and, accordingly, it is difficult to apply them to such fields of use. Thus, plastics materials satisfying the transparency, solvent resistance and heat resistance requirements, among others, imposed on display device substrates, in particular active matrix display device substrates and, at the same time, showing a small coefficient of linear expansion are demanded.
For reducing the coefficient of linear expansion, attempts have been made in the art to produce composite materials by incorporating an inorganic filler, such as a glass powder or glass fiber, in resins. In the case of such resin-inorganic filler composite materials, however, the transparency of the substrates is often impaired. The main cause is the difference in refractive index between the inorganic filler and resin, which causes diffused refraction of the light passing through the resin.
To solve such problems, various methods have been proposed, for example the method comprising adjusting the composition of a styrene-methacrylate copolymer to thereby equalize its refractive index with that of glass fiber, the method of refractive index adjustment which comprises blending an acrylic resin with a styrene-acrylonitrile copolymer and, further, the method of refractive index adjustment which comprises adjusting the composition of an N-substituted maleimide-olefin copolymer (e.g. JP Kokai S54-24993, Japanese Patent Publication (JP Kokoku) H06-94523, Japanese Patent No. 3216179). However, these materials are not sufficient in heat resistance and solvent resistance for their use as active matrix display device substrates in lieu of glass substrates.
It is an object of the present invention to provide a transparent composite composition low in coefficient of linear expansion, excellent in transparency, heat resistance and solvent resistance and capable of serving as a substitute for glass. The composite composition of the invention is suited for use in such fields of application as liquid crystal display device substrates, inclusive of active matrix type ones, organic EL display device substrates, color filter substrates, touch panel substrates, solar cell substrates and like optical sheets, transparent sheets, optical lenses, optical devices, optical waveguides, and LED sealing materials.